Biometric Login in Flutter

A complete guide to implementing secure Face ID and fingerprint authentication in Flutter using the local_auth package.

Step 1: Add local_auth

Step 2: Configuration

Android Setup

Get Ritik’s stories in your inbox

Join Medium for free to get updates from this writer.

Remember me for faster sign in

Update MainActivity.kt

import io.flutter.embedding.android.FlutterActivity X remove
import io.flutter.embedding.android.FlutterFragmentActivity +add…..

class MainActivity: FlutterActivity() X  remove
class MainActivity: FlutterFragmentActivity()  + add…..
{
}

Add this permission in manifest.xml file

<!-- Biometric Authentication Permission Start -->
    <uses-permission android:name="android.permission.USE_BIOMETRIC" />
  <!-- Biometric Authentication Permission End -->

update android/app/src/main/res/values/styles.xml

 <style name="LaunchTheme" parent="@android:style/Theme.Light.NoTitleBar"> X remove 
       <style name="LaunchTheme" parent="Theme.AppCompat.DayNight"> + add….

    <style name="NormalTheme" parent="@android:style/Theme.Light.NoTitleBar"> X remove
    <style name="NormalTheme" parent="Theme.AppCompat.DayNight"> + add…

IOS Setup

To support Face ID on iOS devices, you must add an NSFaceIDUsageDescription entry to your Info.plist file:

NSFaceIDUsageDescription
Explain why your app needs Face ID access here.

Source Code

class BiometricService {
  static final LocalAuthentication localAuth = LocalAuthentication();

 

  static Future<bool> authenticateLocally() async {
    bool isAuthenticate = false;
    try {
      isAuthenticate = await localAuth.authenticate(
          localizedReason: 'We need to authenticate for using this app',
          options: const AuthenticationOptions(
              stickyAuth: true,
              biometricOnly: true,
              sensitiveTransaction: false,
              useErrorDialogs: true));
    } catch (e) {
      AppSnackbar.showSnackBar(message: e.toString());
    }
    return isAuthenticate;
  }


  static Future<void> checkBiometrics() async {
    try {
      final bool canCheck = await localAuth.canCheckBiometrics;
      final bool isSupported = await localAuth.isDeviceSupported();

      final List<BiometricType> biometrics =
          await localAuth.getAvailableBiometrics();

      debugPrint('================================');
      debugPrint('canCheckBiometrics: $canCheck');
      debugPrint('isDeviceSupported: $isSupported');
      debugPrint('availableBiometrics: $biometrics');
      debugPrint('================================');
    } catch (e) {
      debugPrint('Biometric error: $e');
    }
  }
}